1. Technical Field
The present invention relates to an electrophotographic photoreceptor, a process cartridge and an image forming apparatus.
2. Related Art
Generally, an electrophotographic image forming apparatus has the following structure and processes. Specifically, an image-formed material is obtained by charging the surface of an electrophotographic photoreceptor by a charging means in order to impart a desired polarity and a potential to the surface; forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor by selectively discharging the surface and exposing the surface to light in an image-wise manner; developing the latent image by attaching a toner thereto by a developing means to form a toner image; and transferring the toner image onto an image-receiving medium by a transfer means.
Electrophotographic photoreceptors are currently in wide use in the fields of copying machines, laser beam printers and other apparatus, due to such advantages as capability of performing printing at high speed and at high quality. Organic photoreceptors employing an organic photoconductive material have become the mainstream of electrophotographic photoreceptors used in an image forming apparatus, which are more cost effective in production and disposal thereof, as compared with conventionally used electrophotographic photoreceptors employing an inorganic photoconductive material such as selenium, selenium-tellurium alloy, selenium-arsenic alloy, cadmium sulfide, or the like.
A corona charging method utilizing a corona charging device has been conventionally used as a charging method. In recent years, however, a contact charging method, having such advantages as suppressed amounts of ozone production and electricity consumption, has been put to practical application and actively used. In the contact charging method, the surface of an electrophotographic photoreceptor is charged by contacting a conductive member serving as a charging member with the surface of the electrophotographic photoreceptor, or by bringing the conductive member close to the surface of the electrophotographic photoreceptor, and then applying a voltage to the charging member. As the methods of applying a voltage to the charging member, there are a direct current method in which only a direct current voltage is applied, and an alternating current superposition method in which a direct current voltage is applied while superposing an alternating current voltage thereto. The contact charging method has such advantages as downsizing of the apparatus and suppressed generation of harmful gases such as ozone.
As a transfer method, a method of transferring a toner image onto a recording medium via an intermediate transfer member, which is applicable to a wide variety of recording media, has been in wide use in place of a conventionally employed method in which a toner image is directly transferred onto a recording medium.
It is also proposed to provide a protective layer on the surface of an electrophotographic photoreceptor in order to improve the strength of the electrophotographic photoreceptor for preventing deterioration and/or wear of the electrophotographic photoreceptor caused by implementation of a contact charging method, or for preventing occurrence of scratches and/or stabs on the electrophotographic photoreceptor caused by implementation of a direct charging method or the use of an intermediate transfer body, thereby suppressing the amount of electrophotographic photoreceptor leakage (a phenomenon in which an excess local current flows through the electrophotographic photoreceptor).